DISEASES OF THE JOINTS 417 
(b) PurvLent on Suppurative Synovitts. 
In this condition we have synovitis complicated by the 
_ presence of pus. Unlike the simple form, it shows a marked 
- disposition to spread, and quickly involves the surrounding 
structures. Very soon the ligaments of the joint, the peri- 
osteum, the articular cartilages, and the bones are impli- 
cated. This, of course, constitutes a condition of acute 
purulent arthritis. Under that heading, therefore, the con- 
dition will be later discussed. 
B. ARTHRITIS. 
(a) SimpLe orn SeRous ARTHRITIS. 
With an attack of simple synovitis it may be always 
assumed that the changes commenced in the synovial mem- 
brane, communicate themselves more or less readily to the 
surrounding tissues, and are not confined to the synovial 
membrane alone. We may thus have the inflammatory 
phenomena asserting themselves in the surrounding liga- 
ments, in the periosteum, in the bone, and in the articular 
cartilages. It depends, in fact, upon the severity of our 
case whether we call it synovitis or arthritis. The two 
conditions merge so the one into the other that no hard- 
and-fast rule may be laid down whereby they may with 
certainty be differentiated. Such symptoms, therefore, as 
we have given for synovitis may be also read as indicating 
a condition of simple arthritis. The course of the case will 
be very similar, and the treatment to be followed identical 
with that just given. 
(b) AcurE ARTHRITIS. 
Causes.—An attack of acute arthritis may commence with 
the affection of the synovial membrane, and spread from 
that to the other structures. In other cases the disease of 
the synovial membrane, and after it the disease of the joint, 
may be secondary to diseases commencing in the structures 
around the joint. This affection may therefore follow on a 
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